Latinos experience a disproportionate burden of hypokinetic-related chronic diseases, threatening the future health of the nation's fastest-growing population. Physical inactivity has been linked to increased risk of obesity, type 2 diabetes, and various cancers. Latinos are more likely than non-Hispanic whites to fail to meet physical activity (PA) recommendations, and Latino women are less physically active than Latino men. The goal of the proposed ENLACE research project is to design, implement and evaluate a promotora-led PA intervention that takes a comprehensive, multi- level, community-based approach to promoting moderate-to-vigorous physical activity (MVPA) among a particularly underserved segment of Latinas. The intervention approach, based on the social ecological model, focuses on individual attitudes and skills, socio-cultural factors and environmental influences to behavior change. The proposed group- randomized controlled trial builds on formative and pilot research (funded by a National Heart, Lung and Blood Institute R21, HL087765) by a team of academic investigators and community partners with extensive experience working together to conduct behavioral interventions and outreach with Latino and disadvantaged populations. Eight community resource centers (CRCs) in four predominantly Latino counties in South Texas' Lower Rio Grande Valley will be randomly assigned to either the Enlace PA Intervention (4 CRCs) or an attention-control condition (4 CRCs). We will recruit 704 Latinas ages 18-64 who do not meet national PA guidelines from colonias (unincorporated, impoverished, underserved Latino settlements) in the CRC service areas. Participants from CRCs randomized to the Enlace PA Intervention (N = 352; 88 women per CRC) will receive 16 weekly promotora-led group sessions followed by 24 weeks of a maintenance intervention (monthly promotora-delivered newsletters and telephone counseling). The group sessions' behavioral goal is for Latinas to engage in 30 minutes per day of MVPA on 5 or more days per week. The attention- control group (N = 352; 88 women per CRC) will receive 16 weekly promotora-led group sessions on home safety/first aid and monthly generic health education materials and informational telephone calls during the maintenance intervention period. The primary outcome is minutes per week of MVPA (measured with accelerometers). Secondary outcomes are physical fitness and weight maintenance. We also will evaluate self-efficacy, social support, decisional balance, and collective efficacy as mediators of MVPA changes. Standardized measurement of primary and secondary outcomes will occur at baseline, immediate (16 weeks) and delayed post-intervention (40 weeks). We hypothesize that Latinas in the ENLACE PA Intervention will significantly increase their MVPA levels as a result of addressing their specific individual, socio-cultural and environmental barriers and enhancing their social support and collective efficacy, compared to attention-control Latinas.